1. Field of the Disclosure
This disclosure generally relates to a displacement detection device and operating method thereof and, more particularly, to a displacement detection device and operating method thereof that can reduce the system power consumption.
2. Description of the Related Art
Portable electronic devices are popular nowadays for their excellent operating convenience. Most portable electronic devices provide a display screen for a user to watch various application programs and an optical mouse, e.g. an optical finger mouse, for the user to control a cursor or to select an application program to be executed. Reducing the power consumption of the optical mouse is a way to reduce the total power consumption of the portable electronic devices.
Conventionally, it is able to reduce the power consumption of an optical mouse by changing an image capture frequency of the image sensor thereof. For example, U.S. publication No. 20050110746, entitled “Power-saving method for an optical navigation device”, discloses a method for controlling the image capture frame rate of an image sensor according to a moving speed, i.e. variations of a horizontal displacement and a vertical displacement per unit time, of an optical navigation device, wherein when the moving speed is faster, the image capture frame rate becomes higher and the exposure time of the image sensor becomes shorter; on the contrary, when the moving speed is slower, the image capture frame rate becomes lower and the exposure time of the image sensor becomes longer. In this manner, the total power consumption of the optical navigation device can be reduced.
However, the above method, which can reduce the power consumption of an optical navigation device by adjusting the image capture frame rate and the exposure time of an image sensor, still has following problems. (1). Since the exposure time of the image sensor changes with the moving speed of the optical navigation device, the brightness of captured images appears large fluctuation to reduce the stability. (2). Although the image capture frame rate is decreased with the decreasing of the moving speed of the optical navigation device, a sensing region of the image sensor has to be increased so that the maximum detectable acceleration obtained under a low moving speed can be maintained equal to that obtained under a high moving speed. Therefore, the loading of the digital signal processor included in the optical navigation device will not linearly decrease with the decreasing of the image capture frame rate.
Accordingly, the present disclosure provides a displacement detection device and operating method thereof that may control the lighting of a light source according to the detected displacement and eliminate interference from ambient light. Furthermore, the displacement detection device may enter a standby state when no object is detected within a predetermined time interval so as to further save power consumption.